This specification relates to information retrieval.
The Internet provides access to a wide variety of resources, such as image files, audio files, video files, and web pages. A search system can identify resources in response to queries. The queries can be text queries that include one or more search terms or phrases, image queries that include images, or a combination of text and image queries. The search system ranks the resources and provides search results that link to the identified resources. The search results are typically ordered for viewing according to the rank.
The search system may also rank resources based on the performance of the resource with respect to the particular query. For example, some conventional search systems rank resources having a high click-through rate for the particular query higher than resources having a lower click-through rate for the particular query. The general assumption under such an approach is that queries are often an incomplete expression of the information needed, and the user's action of clicking on a particular resource is a signal that the resource is at least as responsive to, or more responsive to, the user's informational need that the other identified resources.